▎ 摘　　要

We present exact results for the electronic transport properties of graphene sheets connected to two metallic electrodes. Our results obtained by transfer-matrix methods are valid for all sheet widths and lengths. In the limit of the large width-to-length ratio relevant to recent experiments, we find a Dirac-point conductivity of 2e(2)/root 3h and a sub-Poissonian Fano factor of 2 - 3 root 3/pi similar or equal to 0.346 for armchair graphene; for the zigzag geometry they are respectively 0 and 1. Our results reflect essential effects from both the topology of graphene and the electronic structure of the leads, giving a complete microscopic understanding of the unique intrinsic transport in graphene.